How to retrieve an element from a set without removing it?

Suppose the following:

>>> s = set([1, 2, 3])

How do I get a value (any value) out of s without doing s.pop()? I want to leave the item in the set until I am sure I can remove it – something I can only be sure of after an asynchronous call to another host.

Quick and dirty:

>>> elem = s.pop()
>>> s.add(elem)

But do you know of a better way? Ideally in constant time.

Answer

Two options that don’t require copying the whole set:

for e in s:
    break
# e is now an element from s

Or…

e = next(iter(s))

But in general, sets don’t support indexing or slicing.